Effect of Cold Deformation and Annealing on Microstructure and Mechanical Properties of 5083 Aluminum Alloy Sheets

Abstract:

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5083 aluminum alloy, due to moderate strength, good thermal conductivity and formability, is an ideal structural material for car production. Influence of cold rolling process on microstructures and mechanical properties of 5083 aluminum alloys is significant and research hotspots. In this paper, cold deformation and annealing processes on grains, tensile properties and anisotropies of 5083 alloy sheets were studied. Results showed that incomplete recrystallization occured on 5083 alloy sheets when annealing temperature was at 300°C. The degree of recrystallization increased slightly with the cold deformation raised from 30% to 50% and varied slightly with prolonged annealing time from 2h to 4h. Furthermore, fully recrystallization occurred on 5083 alloy sheets at the annealing temperature above 320°C. Tensile strength of 5083 alloy sheets reduced significantly when the annealing temperature was raised from 300°C to 320°C, while it varied slightly when the annealing temperature continued to rise to 380°C.

Abstract: Superplastic forming provides a good way for Ti alloys which are usually difficult to
be deformed. Ti75 alloy with a nominal composition of Ti-3Al-2Mo-2Zr is a newly developed corrosion resistant alloy, with a middle strength and high toughness. In the present paper, superplastic behavior of the alloy was investigated, the microstructural evolution in superplastic deformation was observed and the superplastic deformation mechanisms were analyzed. The results showed that the strain rate sensitivity, m, of the Ti75 alloy was larger than 0.3 and the strain was over 2.0 without surface cracking at 800°C and 5×10-4s-1 in compressive testing.
During the first stage of superplastic deformation, a phase grains became equiaxed, fine and homogeneous due to the recrystallization in a phase and diffusion in b phase. Newly formed equiaxed a grains then could slide and rotate, exhibiting superplastic features. The stress concentration caused by grain sliding of a grains could be released by slip and diffusion in b phase between the a phase grains, which acted as accommodation mechanisms.

Abstract: Warm compression tests of AZ31 Mg alloy were carried out at five temperatures in
30°C intervals from 210°C to 330°C. The samples of different thickness which were machined
from as-cast and pre-strained AZ31 billets were compressed into thickness 1mm and then cooled in
the air to room temperature. The microstructural evolution of AZ31 Mg alloy was investigated
during warm compression forming. The results show that all the samples have undergone a
microstructure changes to different scales in the range investigated. The twinning is the
predominant deformation mechanism for magnesium alloys at moderate temperatures and its
occurrence is dependent on temperature and strain. Microstructural evaluation indicates that the
mean size of the recrystallised grains decreases with increasing effective strain and temperature
because of sufficient dynamic recrystallization. The original grain has significant influence on
microstructural evolution during warm forming.

Abstract: The influence of plastic deformation and heat-treatment on the precipitation of Al3(Sc,
Zr) particles and the effect of these precipitates on hardening and softening processes of dilute
ternary Al-0.2wt.%Sc-0.1wt.%Zr alloy was investigated. Behaviour of two differently prepared
alloys (mold cast and prepared by powder metallurgy – PM) was investigated in as-prepared and in
cold rolled state. Both alloys exhibit the same peak age hardening, PM one reaches it already during
extrusion at 350°C. Both cold rolled alloys are highly resistant against recovery, which proceeds
without rapid hardness decrease at high temperatures. Evolution of hardness agrees well with that of
resistivity and with TEM observation.

Abstract: A zircon coating was applied on the surface of Ti-6Al-4V alloy by plasma spray and its
effect on the high temperature tensile properties of the alloy as well as the oxidation behavior of the
alloy were studied. Tensile tests were conducted at 850°C with different strain rates of 10-4s-1,10-3s-
1, 10-2s-1 and 10-1s-1. The results show that the elongation of the coated specimens is higher than that
of the uncoated ones, while the ultimate tensile strength of the alloy is not changed. An oxide film
had formed on the surface of uncoated Ti-6Al-4V alloy, however no such oxide film was found on
the coated alloy at the early of stage. The coating can prevent oxygen penetration into the substrate
thus prevent embrittlement of the subsurface zone. The ductility could be improved by means of the
zircon coating. The optical micrographs of the specimens show little change in microstructures of
the coated and uncoated specimens. Zircon coating has no effect on the microstructure of the
substrate alloy.

Abstract: The effect of Cd and Sb addition on the microstructural and mechanical properties of as-cast AZ31 alloys was investigated and compared. The results indicate that the difference of Sb and Cd in the microstructure and mechanical properties of as-cast AZ31 magnesium alloy is significant. Addition of 0.15%Sb (mass fraction) to AZ31 alloy can refine the matrix and β-Mg17Al12 phase but not form a new phase Mg3Sb2. Oppositely, by addition of 0.3-0.7% Cd to AZ31 alloy, Cd was dissolved into the AZ31 alloy, the phase composition did not change but was refined also. Accordingly, the Cd-refined AZ31 alloy exhibits higher tensile and impact toughness and Brinell hardness properties than the Sb- refined one. The difference of Sb and Cd in the mechanical properties is possibly related to the solid solution of Cd into the matrix and formation of Mg3Sb2 which has the same close-packed hexagonal structure as α-Mg.